---
title: pg_aggregate 
---

The `pg_aggregate` table stores information about aggregate functions. An aggregate function is a function that operates on a set of values \(typically one column from each row that matches a query condition\) and returns a single value computed from all these values. Typical aggregate functions are `sum`, `count`, and `max`. Each entry in `pg_aggregate` is an extension of an entry in `pg_proc`. The `pg_proc` entry carries the aggregate's name, input and output data types, and other information that is similar to ordinary functions.

|column|type|references|description|
|------|----|----------|-----------|
|`aggfnoid`|regproc|pg\_proc.oid|OID of the aggregate function|
|`aggkind`|char| |Aggregate kind: `n` for *normal* aggregates, `o` for *ordered-set* aggregates, or `h` for *hypothetical-set* aggregates|
|`aggnumdirectargs`|int2| |Number of direct \(non-aggregated\) arguments of an ordered-set or hypothetical-set aggregate, counting a variadic array as one argument. If equal to `pronargs`, the aggregate must be variadic and the variadic array describes the aggregated arguments as well as the final direct arguments. Always zero for normal aggregates.|
|`aggtransfn`|regproc|pg\_proc.oid|Transition function OID|
|`aggfinalfn`|regproc|pg\_proc.oid|Final function OID \(zero if none\)|
|`aggcombinefn`|regproc|pg\_proc.oid|Combine function OID \(zero if none\)|
|`aggserialfn`|regproc|pg\_proc.oid|OID of the serialization function to convert transtype to `bytea` \(zero if none\)|
|`aggdeserialfn`|regproc|pg\_proc.oid|OID of the deserialization function to convert `bytea` to transtype \(zero if none\)|
|`aggmtransfn`|regproc|pg\_proc.oid|Forward transition function OID for moving-aggregate mode \(zero if none\)|
|`aggminvtransfn`|regproc|pg\_proc.oid|Inverse transition function OID for moving-aggregate mode \(zero if none\)|
|`aggmfinalfn`|regproc|pg\_proc.oid|Final function OID for moving-aggregate mode \(zero if none\)|
|`aggfinalextra`|bool| |True to pass extra dummy arguments to `aggfinalfn`|
|`aggmfinalextra`|bool| |True to pass extra dummy arguments to `aggmfinalfn`|
|`aggsortop`|oid|pg\_operator.oid|Associated sort operator OID \(zero if none\)|
|`aggtranstype`|oid|pg\_type.oid|Data type of the aggregate function's internal transition \(state\) data|
|`aggtransspace`|int4| |Approximate average size \(in bytes\) of the transition state data, or zero to use a default estimate|
|`aggmtranstype`|oid|pg\_type.oid|Data type of the aggregate function's internal transition \(state\) data for moving-aggregate mode \(zero if none\)|
|`aggmtransspace`|int4| |Approximate average size \(in bytes\) of the transition state data for moving-aggregate mode, or zero to use a default estimate|
|`agginitval`|text| |The initial value of the transition state. This is a text field containing the initial value in its external string representation. If this field is NULL, the transition state value starts out NULL.|
|`aggminitval`|text| |The initial value of the transition state for moving- aggregate mode. This is a text field containing the initial value in its external string representation. If this field is NULL, the transition state value starts out NULL.|

**Parent topic:** [System Catalogs Definitions](../system_catalogs/catalog_ref-html.html)

